b 1. Field of the Invention
The present invention relates generally to an automotive control system which controls suspension system and steering system in combination. More specifically, the invention relates to a control system which controls suspension characteristics depending upon the vehicle driving condition and, as well, controls power assist mode of the power steering system for adjusting assist force.
2. Description of the Background Art
Variable damping force suspension systems have been disclosed in U.S. Pat. No. 4,652,010, issued on Mar. 24, 1987, which has been commonly assigned to the assignee of the present invention, for example. For these suspension systems, control for selecting suspension characteristics detecting on the vehicle driving condition for accomplishing riding comfort, driving stability and suppression of attitude change.
On the other hand, control systems for power steering systems haven been proposed for adjusting hydraulic assist force and whereby for adjusting manual force required for steering operation generally depending upon vehicular driving speed. In the modern power steering control systems, the control systems can operate in various modes, such as heavy, medium and light modes, so that the driver can select steering system control characteristics depending on his own taste.
Such conventional suspension control systems and power steering control systems have been designed for controlling the suspension systems or power assist systems for the power steering systems depending upon instantaneous values of associated control parameters. In order words, the conventional control system detects instantaneous vehicle driving condition with the associated control parameters for determining the control characteristics thereof. However, in order to optimize suspension control characteristics and steering control characteristics, the control characteristics has to be adjusted depending upon the vehicle driving characteristics and driving condition.